TRIGONOMETRY 63 



functions by the root of some quantity, the proper sign may be taken from this 

 table. 



3.10 Functions of Half an Angle. (See 3.05 for signs.) 

 3.101 



3.102 



3.103 



. i Ji 



in -x = V 



2 T 



- COS X 



= - < Vi + sin x T Vi - sin x \ 

 2 I J 



/i/ _' i "\ 



* 2\ Vi + tan 2 x> 



cos - * = 



+ cos x 



= ~ \ Vi + sin a: Vi - sin x 



tan -# = 

 2 



COS # 

 + COS X 



